Assessing the impact of East Coast Fever immunisation by the infection and treatment method in Tanzanian pastoralist systems

A field trial was carried out in a Maasai homestead to assess the impact of East Coast Fever (ECF) immunisation by the infection and treatment method (ITM) with the Muguga Cocktail on the occurrence of this disease in Tanzanian pastoralist systems. These data were further used in partial budgeting and decision analysis to evaluate and compare the value of the control strategy. Overall, ITM was shown to be a cost-effective control option. While one ECF case was registered in the immunised group, 24 cases occurred amongst non-immunised calves. A significant negative association between immunisation and ECF cases occurrence was observed (p≤0.001). ECF mortality rate was also lower in the immunised group. However, as anti-theilerial treatment was given to all diseased calves, no significant negative association between immunisation and ECF mortality was found. Both groups showed an overall similar immunological pattern with high and increasing percentages of seropositive calves throughout the study. This, combined with the temporal distribution of cases in the non-immunised group, suggested the establishment of endemic stability. Furthermore, the economic analysis showed that ITM generated a profit estimated to be 7250 TZS (1 USD=1300 TZS) per vaccinated calf, and demonstrated that it was a better control measure than natural infection and subsequent treatment.     

Immunisation against Theileria parva in eastern Zambia: influence of maternal antibodies and demonstration of the carrier status

Immunisation of calves by the infection and treatment method (I & T) has been extensively used in the eastern province of Zambia to control East Coast fever (ECF), a protozoan tick-borne disease. This paper presents the results of a field longitudinal study, which included a total of 148 Angoni calves. After immunisation against ECF, they were monitored for a full rainy season, coinciding with the main peak of activity of the vector of Theileria parva, the tick Rhipicephalus appendiculatus. Dysimmunisation (acute reaction generated by I & T immunisation), seroconversion and mortality are among the parameters recorded. The effect of maternal antibodies on these parameters was analysed and also studied in experimental conditions on two calves. Before immunisation, young calves had a higher seroprevalence than older animals (maternal antibodies) but their post-immunisation seroprevalence was lower. There was no evidence that their immunoprotection was weaker but this indicates that the post-immunisation seroconversion is probably not a reliable tool to monitor the efficacy of calf immunisation. The carrier state of cattle after immunisation was investigated in experimental conditions on three bovines whereas in the field, the infection prevalence in the ticks was estimated using the relation between the tick burden and the T. parva contacts with the calves. The ability of larval and nymphal R. appendiculatus ticks to pick-up T. parva from carriers and to transmit it to na?ve animals after moulting was assessed. It was found that both instars are able to transmit clinical and lethal ECF but that the prevalence of T. parva infection in nymphs is much lower than in adults, confirming the primary role of adults in the transmission of ECF in endemic conditions. Similar results were obtained from the field whereby the ECF peak corresponds with the peak of adult R. appendiculatus activity. The infection prevalence in the ticks was however much lower in the field than in experimental conditions indicating that an important proportion of them feed on alternative hosts. Old ticks seemed to have lost part of their infectivity.     

East Coast fever immunisation field trial in crossbred dairy cattle in Hanang and Handeni districts in northern Tanzania

East Coast fever (ECF) causes considerable mortality and production losses in the Tanzania smallholder dairy sector and limits the introduction of improved dairy breeds in areas where the disease is present. The infection and treatment method (ITM) was adopted by smallholder dairy farms for ECF immunisation in Hanang and Handeni districts of Tanzania. This study recorded incidence rates for ECF and other tick-borne diseases (TBDs) for ECF-immunised and non-immunised cattle between 1997 and 2000. Approximately 80% of smallholder households from both sites (n?=?167) participated in this longitudinal study, with immunisations carried out at the request of the livestock owners. Efficacy of ITM for preventing ECF cases in these crossbred dairy cattle was estimated at 97.6%, while that for preventing ECF deaths was 97.9%. One percent of the cattle developed clinical ECF as a result of immunisation. Since ECF immunisation permits a reduction in acaricide use, an increase in other TBDs is a potential concern. Sixty-three percent of farmers continued to use the same acaricide after immunisation, with 80% of these reducing the frequency of applications. Overall, 78% of farmers increased the acaricide application interval after immunisation beyond that recommended by the manufacturer, resulting in annual savings in the region of USD 4.77 per animal. No statistical difference was observed between the immunised and non-immunised animals in the incidence of non-ECF TBDs. However, immunised animals that succumbed to these diseases showed fewer case fatalities. ITM would therefore appear to be a suitable method for ECF control in Tanzania's smallholder dairy sector.     

An evaluation of the relative efficacy of a new formulation of oxytetracycline for the treatment of undifferentiated fever in feedlot calves in western Canada

A field trial was performed under commercial feedlot conditions in western Canada to compare the efficacy of a new formulation of long-acting oxytetracycline (LA 30) to a standard long-acting oxytetracycline formulation (LA 20) and florfenicol (FLOR) for the treatment of undifferentiated fever (UF) in calves that received metaphylactic tilmicosin upon arrival at the feed-lot. Seven hundred and ninety-seven recently weaned, auction market derived, crossbred, beef calves suffering from UF were allocated to 1 of 3 experimental groups as follows: LA 30, which received intramuscular long-acting oxytetracycline (300 mg/mL formulation) at the rate of 30 mg/kg body weight (BW) at the time of allocation; LA 20, which received intramuscular long-acting oxytetracycline (200 mg/mL formulation) at the rate of 20 mg/kg BW at the time of allocation; or FLOR, which received intramuscular florfenicol administered at the rate of 20 mg/kg BW at the time of allocation and again 48 hours later. Two hundred and sixty-six animals were allocated to the LA 30 group, 265 animals were allocated to the LA 20 group, and 266 animals were allocated to the FLOR group. The relative efficacy of the LA 30 group, as compared with the LA 20 and FLOR groups, was assessed by comparing relapse, chronicity, wastage, and mortality rates. The overall mortality (RR = 0.50) rate in the LA 30 group was significantly (P < 0.05) lower than in the LA 20 group. However, the overall chronicity (RR = 2.56) and overall wastage (RR = 6.97) rates of the LA 30 group were significantly (P < 0.05) higher than in the LA 20 group. There were no significant (P > or = 0.05) differences in UF relapse rates or cause specific mortality rates between the LA 30 and LA 20 groups. In the economic analysis, there was an advantage of $28.59 CDN per animal in the LA 30 group compared with the LA 20 group. The overall chronicity (RR = 2.25) and overall wastage (RR = 2.80) rates of the LA 30 group were significantly (P < 0.05) higher than the FLOR group. There were no significant (P > or = 0.05) differences in UF relapse rates, overall mortality rates, or cause specific mortality rates between the LA 30 and FLOR groups. In the economic analysis, there was an advantage of $12.90 CDN per animal in the LA 30 group compared with the FLOR group. In summary, the results of this study indicate that it is more cost-effective to use a new formulation of long-acting oxytetracycline (300 mg/mL formulation administered at a rate of 30 mg/kg BW) than a standard long-acting oxytetracycline formulation (200 mg/mL formulation administered at a rate of 20 mg/kg BW) or florfenicol for the treatment of UF in feedlot calves that have previously received metaphylactic tilmicosin upon arrival at the feedlot.     

Immunisation of cattle against theileriosis in Nakuru District of Kenya by infection and treatment and the introduction of unconventional tick control.

One hundred and one cross European-Boran cattle (50 cows and 51 calves), on a farm in Nakuru District, Kenya, were immunised against theileriosis using Theileria parva lawrencei and Theileria parva parva stocks from another district of Kenya. The stabilates used were T.p.lawrencei (Mara III) used at 10(-1.7) dilution and T.p.parva (Kilae) used at 10(-1.0) dilution. The stabilates were combined and inoculated simultaneously with a short-acting formulation of oxytetracycline hydrochloride given intramuscularly at 10 mg kg-1 body weight and was repeated on Day 4 after inoculation of the stabilate. Most of the theileriosis challenge on the farm was thought to be derived directly from the African buffalo (Syncerus caffer). Nine percent of the cattle had significant indirect fluorescent antibody (IFA) titres before the immunisation and 99% after immunisation. The immunised cattle were exposed to tick-borne disease challenge on the farm by withdrawal of acaricide cover. The immunised cattle were divided into five groups plus two susceptible control cows and two calves for each group. Cattle in four of the groups had acaricidal ear tags, each group having a different type, applied to both ears and the fifth group remained untagged. The animals remained without conventional acaricide application for 134 days. Ten out of 20 (50%) non-immunised control cattle became T.p.lawrencei reactors which only one out of 97 (1%) of the immunised cattle reacted. A frequent complication noted was mild infections due to unidentified Theileria sp. which required expert differentiation from T.parva infections. An additional group of ten steers whose tick load was removed by hand at weekly intervals was introduced 79 days after exposure; these had no tick control and four became T.p.lawrencei reactors. Of 12 calves born during the exposure period and without tick control, four became theilerial reactors and one died. The application of acaricidal tags however, reduced tick infestation levels considerably compared with untagged controls but did not prevent transmission of theileriosis with the possible exception of tags on Group 4. A number of transient low grade fevers were noted and attributed to Theileria sp., Ehrlichia bovis, Ehrlichia (Cytoecetes) ondiri and Borrelia theileri infections, none of which were fatal. One immunised animal died of acute dual infection of Babesia bigemina and Borrelia theileri after acaricide control by spraying was re-introduced but no Anaplasma infections were detected. An analysis of the economic effects of immunisation was made.     

Comparison of long acting oxytetracycline and parvaquone in immunisation against East Coast fever by infection and treatment

Two groups of five cattle were immunised with a field isolate of Theileria parva as stabilate and simultaneously treated with long acting oxytetracycline or parvaquone in early clinical disease. The oxytetracycline group suffered a marked fall in leucocyte count and one animal died during immunisation. The parvaquone group suffered a less severe fall in leucocyte count and all survived. The surviving immunised cattle were immune to homologous challenge but susceptible to subsequent challenge with T p lawrencei.     

Financial analysis of East Coast fever control strategies in traditionally managed Sanga cattle in Central Province of Zambia

Five different East Coast fever (ECF)-control strategies (involving ECF immunisation by the infection-and-treatment method) were tested in groups of traditionally managed Sanga cattle in the Central Province of Zambia over a period of 2.5 years. Two groups were under intensive tick control (weekly spraying with acaricide)--one group immunised and the other non-immunised. Two groups were under no tick control--one group immunised and the other non-immunised. The fifth group was under seasonal tick control (18 sprays/year) and was immunised against ECF. The input and output data were used to construct discounted cash flows for each group. The seasonally sprayed and immunised group gave the highest net present value, and the non-immunised group with no tick control, the lowest. A break-even analysis showed that the immunisation costs could rise to US$25.9 per animal before profitability was affected. For herds under intensive tick control, immunisation was of no financial benefit. The results demonstrate the value of immunisation, and indicate the importance of its combination with seasonal tick-control measures.     

Epidemiological observations on theileriosis following field immunisation using infection and treatment

Thirty-seven high grade cattle were immunised against Corridor disease (Theileria parva lawrencei infection) on a farm with a history of heavy and often lethal theilerial challenge. Nineteen cattle were immunised by treating with two doses of long-acting oxytetracyclines given at 20 mg/kg on days 0 and 4 after sporozoite stabilate inoculation, while the other 18 were treated with naphthoquinone buparvaquone, given as a single dose of 2.5 mg/kg simultaneously with stabilate inoculation. All the cattle underwent subclinical theilerial reactions with all but two developing high antibody titres on the IFAT test against T. parva schizont antigen by day 35 after the immunisation. Both buparvaquone and long-acting oxytetracycline appeared equally effective in the immunisation. To date, 26 months later, only two cases of theileriosis parasitologically characteristic of T. p. parva have been reported in the immunised cattle. Following the two cases, investigations showed that when uninfected Rhipicephalus appendiculatus nymphal ticks were deliberately fed on healthy resident cattle on the farm, the resultant adult ticks transmitted acute and lethal theilerial infections to five out of five susceptible cattle. The resultant infections were parasitologically characteristic of T. p. parva infections. Furthermore, the monoclonal antibody profiles of schizont infected cell lines from these infections appeared to be characteristic of T. p. parva. It was thus concluded that resident cattle on the farm could be a potential source of T.p. parva infection which had broken through the immunity of T.p. lawrencei immunised cattle and could constitute a reservoir of theilerial infection for ticks and hence to susceptible stock on the farm.     

Immunisation of cattle against theileriosis in Coast Province, Kenya: laboratory evaluation of a Theileria parva parva stabilate for use in 'infection and treatment' immunisation in the field

Theileria parva parva Marikebuni stock, previously shown to give good protection to immunised cattle in Kilifi District, Coast Province of Kenya, was chosen for large scale immunisation in the district. A large sporozoite stabilate was prepared and evaluated for efficacy and safety in the 'infection and treatment' method, using a long or short acting formulation of oxytetracycline. Susceptible cattle were infected with selected doses of stabilate (10(0), 10(-1), 10(-1.7) and left either as untreated controls, or treated with one of the two oxytetracycline formulations. It was concluded that stabilate dilution at 10(-0.7) or 10(-1) in combination with either formulation of oxytetracycline would effect satisfactory immunisation. The short acting oxytetracycline treatment was judged to be the most efficacious in protecting cattle against homologous challenge. On heterologous challenge it was found that T p parva Marikebuni immune cattle were protected against seven T p parva stocks from Kilifi District and also against four stocks of T p parva from other areas of Kenya. In addition, the Marikebuni stock provided partial protection against challenge by T p lawrencei stocks. Furthermore, cattle immune to T p parva and T p lawrencei were protected against lethal challenge of T p parva Marikebuni stock. Thus, it appears that large scale immunisation of cattle against theileriosis in Kilifi District could be undertaken using the Marikebuni stock. With continued assessment, this stock could provide a master theilerial stock for immunisation against cattle theileriosis in areas free of buffaloes elsewhere in Kenya.     

Efficacy of long-acting oxytetracycline for the prevention of tick-borne fever in calves

Twenty-six calves which had not previously grazed tick-infested pasture were divided into two equal groups. On May 26, 1988 (day 0) they were turned out into a field of rough grazing where cases of redwater fever had occurred the previous spring. Seven, 14, 21 and 28 days after the start of the trial the animals in one group each received an intramuscular injection of 20 mg/kg bodyweight of long-acting oxytetracycline. During the 60 days of the trial the animals received a severe tick-borne fever challenge, in some cases combined with a redwater fever challenge. An unforeseen complicating factor was the presence of animals persistently infected with bovine viral diarrhoea virus, present in almost equal numbers in both groups. At the end of the trial the treated group weighed on average 16 kg more than the control group, a difference which was attributed to the suppression of tick-borne fever by oxytetracycline.     

Treatment of Moraxella bovis infections in calves using a long-acting oxytetracycline formulation

George, L.W. & Smith J.A. Treatment of Moraxella bovis infections in calves using a long-acting oxytetracycline formulation. J. vet. Pharmacol. Therap. 8, 55–61.
Studies were undertaken to determine the effectiveness of an oxytetracycline HCl formulation for the prophylaxis and treatment of chronic Moraxella bovis ocular infections in calves. Two separate experiments were performed. For the first, calves were separated into two groups and the eyes were infected with M. bovis. The eyes of these calves were observed and cultured for 37 consecutive days. On the 37th and 40th day, each of the five calves were treated intramuscularly with the drug (20 mg/kg of body weight). The other five calves (second group) remained untreated as controls. The cultures from the five treated calves were negative after the first antibiotic administration and remained so for 14 days. M. bovis was isolated from each eye of the control calves at least once during that time. None of the antibiotic-treated calves was completely resistant when reinfected with M. bovis. For the second experiment, calves were given a prophylactic administration of the formulation and were then infected with M. bovis 48 ( n = 4 calves) or 72 ( n = 4 calves) h later. These treatments resulted in a lower incidence of keratoconjunctivitis and a decreased duration of bacterial shedding, as compared to controls ( n = 8 calves), but did not completely prevent the occurrence of disease or the establishment of ocular infections.
Lisle W. George, Department of Medicine, School of Veterinary Medicine, University of California, Davis, CA 95616, U.S.A.     

A comparison of prophylactic efficacy of tilmicosin and a new formulation of oxytetracycline in feedlot calves

Two replicated-pen field studies were performed under commercial feedlot conditions in western Canada to compare the administration of long-acting oxytetracycline at 30 mg/kg body weight (BW) versus tilmicosin at 10 mg/kg BW to feedlot calves upon arrival at the feedlot. Ten thousand nine hundred and eighty-nine, recently weaned, auction market derived, crossbred beef steer and bull calves were randomly allocated upon arrival at the feedlot to one of 2 experimental groups as follows: oxytetracycline, which received intramuscular long-acting oxytetracycline (300 mg/mL formulation) at a rate of 30 mg/kg BW; or tilmicosin, which received subcutaneous tilmicosin (300 mg/mL formulation) at a rate of 10 mg/kg BW. There were 20 pens in each experimental group. In Study 1 and in the combined analysis, the initial undifferentiated fever (UF) treatment rate was significantly (P < 0.05) higher in the oxytetracycline group as compared with the tilmicosin group. There were no significant (P > or = 0.05) differences in first UF relapse, second UF relapse, third UF relapse, overall chronicity, overall rail, overall mortality, bovine respiratory disease (BRD) mortality, hemophilosis mortality, arthritis mortality, or miscellaneous mortality rates between the experimental groups in either study or in the combined analysis. In addition, there were no significant (P > or = 0.05) differences in initial weight, final weight, weight gain, days on feed, daily dry matter intake, average daily gain, or the dry matter intake to gain ratio between the experimental groups in either study or in the combined analyses. In the economic analysis, there was a net economic advantage of $5.22 CDN per animal in the oxytetracycline group, due to a lower prophylactic cost, even though the UF therapeutic cost was higher.     

Identification of a target population for immunisation against East Coast fever in coastal Kenya

Two experiments were carried out to identify the target population of cattle for immunisation against East Coast fever (ECF) using the infection-and-treatment method. Firstly, a sentinel-calf study was used to determine the age window for ECF immunisation by determining ages at clinical detection of infection with Theileria parva. Six groups of five naive cross-bred (Bos taurus/Bos indicus) male calves, introduced at intervals of 2 months at a mean age of 26 days, were exposed to natural tick challenge on a high ECF-risk, small-holder farm in the coastal lowland, coconut-cassava agro-ecological zone of coastal Kenya. Secondly, a challenge study evaluated the relationship between the presence of T. parva antibodies and immunity. Ten indigenous adult Zebu cattle and nine Zebu young stock purchased from farmers in the same zone, and eight cross-bred calves (survivors of the sentinel-calf study) were challenged with 10 times the immunising dose of T. parva Marikebuni stock. Twenty-four of these 27 cattle had high antibody titres before challenge. Two cross-bred calves, obtained from an ECF-free area and seronegative to T. parva schizont antigen, also were challenged and used as susceptible controls. Twenty-five (83%) of the 30 sentinel calves contracted ECF over an age range of 36-116 days (mean 72 days). The remaining five calves died of other causes within 2 months of arrival on the farm. Fourteen of the 25 calves survived the infection and developed antibodies to T. parva. Despite tick control, seven of these 14 calves had a second episode of ECF and two died. In total, 13 of the 25 calves that contracted ECF died. Only one of 19 indigenous Zebu animals developed clinical ECF when challenged with T. parva Marikebuni (mild clinical signs with spontaneous recovery). Of the eight cross-bred survivors from the first experiment, only one succumbed to ECF when challenged and it died. Both susceptible cross-bred calves developed severe clinical signs of ECF and one died. The experimental studies show that in the high ECF-risk areas of the coconut-cassava zone of coastal Kenya, immunisation against ECF in cross-bred (B. taurus/B. indicus) cattle should be targeted at an early age (preferably within 1-2 months of birth).     

Development and duration of protection against salmonellosis in mice and sheep immunised with live aromatic-dependent Salmonella typhimurium.

The aim of this investigation was to determine the development and duration of protection in mice or sheep immunised with aromatic-dependent (aro-) Salmonella typhimurium strain CS332, by either parenteral or oral routes. Immunisation of mice by the intraperitoneal or sheep by the intramuscular routes was found to impart protection against oral challenge with the virulent parent S typhimurium strain CS94 as early as seven days after immunisation. In contrast, when immunisation was carried out by the oral route, protection was not evident until three weeks after immunisation. Regardless of the route of immunisation, mice were still partially protected at three months and were fully susceptible at six months after immunisation. In sheep, protection persisted for six months but not 12 months after immunisation. Only parenterally immunised mice and sheep developed high ELISA and, or, agglutinating antibody titres, and cutaneous delayed-type hypersensitivity (DTH) at three weeks after immunisation. Although both antibody and DTH were detectable three months after immunisation of mice with aro- S typhimurium strain CS332, none was detected at six months. Antibody measured by agglutination and ELISA was detectable six months after immunisation in sheep, although no DTH was evident. At 12 months after immunisation low levels of anti-LPS antibody (measurable by ELISA only) were detected in sheep immunised by the intramuscular route.     

Effect of vaccination of cattle with the low virulence Nc-Spain 1H isolate of Neospora caninum against a heterologous challenge in early and mid-gestation

Live vaccines have emerged as one of the most potentially cost-effective measures for the control of bovine neosporosis. Previous studies have shown that Nc-Spain 1H is a naturally attenuated isolate of Neospora caninum and that immunisation with live Nc-Spain 1H tachyzoites generated a protective immune response in mice. The aim of this study was to evaluate the safety and efficacy of immunisation in cattle. N. caninum-seronegative heifers were immunised subcutaneously twice with 10⁷ live Nc-Spain 1H tachyzoites prior to artificial insemination. No adverse reactions or negative effects on reproductive parameters were recorded following immunisation. In immunised and non-challenged heifers, no foetal deaths were observed, and none of the calves was congenitally infected. The efficacy against N. caninum-associated foetal death and vertical transmission was determined after challenge with high doses of the Nc-1 isolate at 70 and 135 days of gestation, respectively. After the challenge in early gestation, the immunisation induced a protection of 50% against foetal death. In addition, the microsatellite analysis performed in PCR-positive tissue samples from foetuses that died after challenge infection showed that the profiles corresponded to the challenge isolate Nc-1. A degree of protection against vertical transmission was observed after challenge at mid-gestation; calves from immunised heifers showed significantly lower pre-colostral Neospora-specific antibody titres than calves from the non-immunised/challenge group (P < 0.05). Strong antibody and interferon gamma responses were induced in the immunised heifers. This study indicates that the immunisation before pregnancy with the Nc-Spain 1H vaccine isolate appeared to be safe and reduced the occurrence of N. caninum-associated abortion and vertical transmission in experimentally infected cattle. In light of these encouraging results, the next step for testing this live attenuated candidate should be the assessment of its efficacy and safety in naturally infected cattle.     

Kinetics and type of immune response following intranasal and subcutaneous immunisation of calves

Protection of animals against respiratory infections has long been known to depend on respiratory mucosal immunity. However, few studies have been reported on the immune response following intranasal (i.n.) immunisation with non-living, soluble antigens. This study determined the kinetics of the humoral and cellular immune responses in calves after i.n. immunisation with Limulus haemocyanin (LH) with cholera toxin adjuvant, or subcutaneous (s.c.) immunisation with LH in incomplete Freund's adjuvant. A proliferative response of peripheral blood mononuclear cells cultured in vitro with LH was observed in animals immunised 7-10 days after i.n. and s.c. immunisations with no significant differences between the two immunised groups. LH -specific antibody was present in the serum of animals immunised s.c. (IgM, IgG1 and IgG2) and i.n. (IgA). Although significant IgA responses were observed, i.n. immunisations in cattle with soluble protein antigens and cholera toxin as an adjuvant did not induce a strong systemic immune response.     

Distribution of oxytetracycline into ocular tissues and tears of calves

A long-acting oxytetracycline formulation was administered (20 mg/kg of body weight) intramuscularly to calves, and the concentrations of the drug in serum, ocular tissues and tears were measured. The drug was distributed selectively to the epithelium of the conjunctiva and to the lacrimal gland ductules, and reached concentrations in each tissue that exceeded those in serum. The drug did not penetrate into the aqueous humour, and produced mean peak lacrimal fluid concentrations less than 1 microgram/ml after i.m. administration. When given subconjunctivally, however, concentrations greater than 2.0 micrograms/ml were observed in tears for 72 h. Severe local reactions occurred in all calves that were given the drug subconjunctivally.     

Chemoimmunoprophylaxis against bovine tropical theileriosis in young calves: a comparison between buparvaquone and long-acting oxytetracycline

Eighteen seven to 21-day-old crossbred (Bos taurus cross Bos indicus) calves were allocated to four groups (A to D). Groups A and B each consisted of six calves and groups C and D three calves each. Each calf in groups A, B and C was inoculated with ground-up tick supernate (GUTS) equivalent to two infected acini prepared from Theileria annulata-infected Hyalomma anatolicum anatolicum. Each calf in group A was also given a single intramuscular injection of buparvaquone, 2.5 mg kg-1 bodyweight simultaneously with GUTS, whereas each calf in group B was given a single intramuscular injection of long-acting oxytetracycline, 20 mg kg-1 bodyweight following inoculation of GUTS. In calves of group A clinicopathological reactions were negligible, whereas in calves of group B mild to severe reactions were observed resulting in the death of three of the six calves. All the calves of group C (infected, untreated controls) died of acute theileriosis. All the surviving calves of groups A and B withstood a lethal homologous challenge given on day 30 after immunisation, indicating no difference in the immune status of the surviving calves of the two groups. Group D, challenge control, all calves died of theileriosis within 18 days of challenge.     

A field study of the effects of a monovalent Leptospira borgpetersenii serovar Hardjo strain hardjobovis vaccine administered with oxytetracycline on reproductive performance in beef cattle

OBJECTIVE: To determine whether vaccination with a monovalent Leptospira borgpetersenii serovar Hardjo strain hardjobovis vaccine coupled with parenteral long-acting oxytetracycline treatment would improve the reproductive performance of beef cows. DESIGN: Randomized controlled field trial. ANIMALS: 1,446 Angus-cross beef cows in 8 locations. PROCEDURES: Cows were given 2 doses, 4 weeks apart, of vaccine (treatment; n=741) or placebo (control; 705). Cows in the treatment group were also given a single dose of a long-acting oxytetracycline formulation (20 mg/kg [9.1 mg/lb], SC) at the time of booster vaccination. Estrus synchronization was performed, followed by fixed-time artificial insemination; bulls were introduced 14 days after insemination. Serum and urine samples were obtained on a random subset of cows (n=194) for detection of serologic titers and leptospiruria, and locations were categorized as positive or negative for leptospirosis on the basis of detection of leptospiruric cows. RESULTS: No differences in pregnancy and calving rates between treatment and control groups were detected. Pregnancy rate following artificial insemination was lower among cows in locations positive for leptospirosis than among cows in locations negative for leptospirosis; however, overall pregnancy rate, calving rate following artificial insemination, and overall calving rate did not differ between groups when cows were grouped on the basis of location leptospirosis status. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggested that under the conditions of the present study, administration of a monovalent Leptospira vaccine in conjunction with systemic administration of oxytetracycline did not significantly improve reproductive performance of beef cows.     

Treatment of acute ocular Moraxella bovis infections in calves with a parenterally administered long-acting oxytetracycline formulation

Acute ocular Moraxella bovis infections were induced in the UV-irradiated eyes of 10 calves. Eight calves developed corneal ulcers in at least 1 eye and were used for the treatment experiment. One randomly selected group of 4 calves with corneal ulcers and M bovis infections in 7 eyes was given a long-acting oxytetracycline formulation in 2 IM dosages of 20 mg/kg of body weight each, 72 hours apart. The other 4 calves with corneal ulcers in 6 eyes and M bovis in all 8 eyes served as nontreated controls. Bilateral ocular cultures were obtained and clinical observations were made daily for 20 days after treatment. After administration of the long-acting drug, new ulcers did not develop in the treated calves, whereas 5 new ulcers developed in the control-group calves during this time. The average durations of increased lacrimation/ulcerated eye were 2 and 12 days after treatment in the treatment and control groups, respectively; the average durations of blepharospasm were 3 and 8 days, respectively. Moraxella bovis was not isolated from any of the eyes of the treatment-group calves for the first 6 days after the antibiotic was administered, but was isolated from 1 eye of 1 treated calf on posttreatment day 7 and daily thereafter, for a total of 14 positive cultures of 160 ocular cultures obtained from the treatment-group calves after treatment. The bacterium was isolated from all eyes and from 144 of 160 cultures from the control-group calves during this time.